Means for and method of defrosting refrigerating apparatus



O 18, 7- M. G. LEESON ,4 0, 3 MEANS FOR AND METHOD OF DEFROSTING REFRIGERATING APPARATUS Filed May 29, 1945 Fie.1

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CONIYDENEER. 6L4 @4 Patented Nov. 18, 1947 UNITED S MEANS FOR AND METHOD OF DEFROSTING REFRIGERATING APPARATUS Meldon G. Leeson, York, Pa... assignor to York Corporation, York, Pa., a corporation of Dela.-

ware

Application May 29, 1945, Serial No. 596,524

Claims.

This invention relates to refrigeration and particularly to a method of and means for defrosting an evaporator which is normally operated at sub-freezing temperatures.

The invention may be applied to any refrigerative circuit having a condenser cooled by flowing fluid, such as water or air, at a temperature substantially above 32 F., and is particularly useful because it may be applied to systems having a single evaporator.

The invention derives the heat needed to defrost the evaporator from the stream of fluid used to cool the condenser; In this way rapid defrosting is secured without the use of a special heater.

Generally stated, the procedure is to stop the compressor (or its equivalent), keep the condenser cooling fluid flowing, and connect the vapor space of the condenser freely with the evaporator, while permitting liquid refrigerant to drain freely from the evaporator to the condenser or receiver, that is to say to some part of the circuit Which normally is part of the high-side and adapted to retain liquid.

Since the frost holds the evaporator at a lower temperature than the condenser, refrigerant will boil in the condenser, flow to the evaporator in the vapor phase, and there condense. The liquid resulting from such condensation drains to the condenser or receiver, while the frost will be thawed by the heat given up by the condensing liquid.

This action continues at a rapid rate until the frost is all melted, and then ceases, whereupon normal connections are restored and the refrigerating cycle is resumed.

The heat for defrosting is furnished by the cooling Water, Without loss, because the refrigerative elfect of the frost is recaptured and de1ivered to the high-side as cold condensed liquid,

The defrosting system is therefore extremely simple in its mechanical aspects and remarkably economical. It also is conspicuously safe because the defrosting heat is supplied at a low temperature.

Preferred embodiments of the invention will now be described by reference to the accompanying drawing, the purpose being to disclose the principle of the invention rather than the mechanical details which can and preferably do conform to standard designs.

In the drawings:

Fig. l is a diagram of a water-cooled system of the compressor-condenser-evaporator circuit type with the invention applied.

Fig. 1.

Fig. 4 is a diagram of a typical control for the compressor and defrosting valves of Fig. 3.

Referring first to Fig. 1, the compressor 6 driven by motor I through a belt discharges through line 8 into a combined condenser and receiver 9. This is of the shell-and-tube type in which cooling water entering at l I, flows through the tubes I2 and discharges at l3. The supply of cooling water is controlled by valve M which is biased to close and is urged in an opening direction by pressure motor 15 which is subject to head pressure in line 8 transmitted by tube It. Control of cooling water in response to head pressure is familiar practice.

A combined condenser and receiver. is used as the most convenient way of assuring that at least some of the water tubes 52 are in heatexchanging relation with liquid refrigerant. Any other arrangement attaining this end'is workable.

The liquid line ll leads from the lower portion of the condenser-receiver 9, through expansion valve E8 to evaporator 59, here diagrammed as a simple sinuous coil. From the lower end of evaporator l9 leads a vertical drain line 2i and to the top of this the compressor suction line 22 is connected, so as to be protected against the entrance of refrigerant in the liquid phase.

A thermal bulb 20 subject to the temperature of refrigerant leaving coil l9 controls valve l8, so that refrigerant leaves evaporator IS in a slightly super-heated state, when the system is operating normally and valve 58 is in control.

The drain line 2| is shown as of considerable diameter to assure free drainage flow of liquid. Interposed in the line 2!, preferably at a level below suction line 22, is a normally closed valve 23 which is opened when a related solenoid 24 is energized. The line 2| is shown offset at the valve simply to permit installation of the valve in a preferred position.

From the lower end of line 2i a connection 25 leads to liquid line H, and in efiect to the liquid space in the condenser.

A normally closed valve 26 controls a by-pass around the water-control valve l4 and is opened when solenoid 21 is energized.

A branch line 28 leads from line 8 and consequently from the vapor space in condenser 9,

through normally closed valve 29, past expansion valve l8 to the upper portion of evaporator l9. Valve 29 is opened by solenoid 3| when the latter is energized.

Under normal conditions the motor I runs and the solenoids 3|, 24 and 21 are de-energized so that their related valves 29, 23 and 26 are closed. To defrost, the motor is stopped and the solenoids are energized to open their respective valves. A simple switch 32 is diagrammed in Fig. 2.

Normally the system operates as an ordinary compressor-condenser-evaporator circuit. When defrosting is necessary, switch 32 is .shifted to stop motor I and open valves 23, 21 and 29, This assures a full flow of water through the condenser. Since the evaporator is at sub-freezing temperature, liquid refrigerant in condenser 9 boils, absorbing its latent heat of vaporization from the cooling water. The vaporized refrigerant flows to the evaporator and there condenses. The heat so released thaws the frost and the condensed refrigerant drains through line When the frost is melted oil, the switch 32' i returned to its original position. It may be actuated manually or by timing or other automatic controls, according to familiar principles.

Fig. 3 shows how the invention may be applied to a circuit having a condenser, cooled by air at temperatures materially above 32 F. Parts identical with parts in Fig. 1 have the same reference numerals increased by 100.

For the parts 9 to I6, 26 and 2'! are substituted a finned coil 35 and motor 36 driving blower 31 which circulates air over coil 35. The operation is the same as that described with reference to Fig. 1, except that the heat is furnished through the condenser b circulated air instead of water.

A simple control for the apparatus of Fig. 3 is diagrammed in,,1=ig. 4. Switch I32 does not control motor 36, but does control motor I01 and solenoids I24 and .l3l, so that the motor runs when the solenoids are de-energized and stops when they are energized.

The drain line 2| (or i2!) is liquid sealed at its lower end, and is so located that liquid drains (to a point below valve 23 (or I23) and hence can never be drawn into the compressor.

In both illustrated embodiments a motor-driven compressor is shown as the means to withdraw refrigerant from the evaporator and deliver it at higher pressure to the condenser, but any controllable means to perform this function may be used. It takes no part in the defrosting cycle, and all that is necessary is that its operation be capable of suspension during defrosting.

What is claimed is:

1. The method of defrosting the evaporator of a refrigerating circuit containing a volatile refrigerant and including an evaporator, a refrigerant-liquid retaining condenser with which a cooling fluid materially above 32 F. flows in heatexchanging relation, energy-operated means for withdrawing vaporous refrigerant from the evaporator and delivering it at higher pressure to the condenser, and expansion means for delivering liquid refrigerant from the condenser to the evaporator while maintaining a pressure differential; said method comprising, suspending the operation of the energy-operated means and continuing the flow of condenser-cooling fluid whiletemporarily affording paths for free flow of refrigerant vapor from the condenser to the evaporator and free drainage of liquid from the evaporator to the condenser.

2. The method of defrosting the evaporator of a refrigerating plant of the compressor-condenser-evaporator circuit type having a refrigerant-liquid retaining condenser cooled by a fluid flowing at a temperature materially above 32 R; which method comprises, stopping the compressor and continuing the flow of condenser-cooling fluid while temporarily affording paths for free flow of vapor from the condenser to the evaporator and free drainage of liquid from the evaporator to the condenser.

3. The combination of a refrigerating circuit containing a volatile refrigerant and comprising an evaporator, a liquid-refrigerant retaining condenser, means for circulating a cooling fluid at a temperature materially above 32 F. in heatexchanging relation with liquid in the condenser, energy-actuated means for withdrawing refrigerant vapor from the evaporator and delivering it at higher pressure to the condenser, and means serving to maintain a pressure differential between the condenser and the evaporator while supplying liquid refrigerant from the former to the latter; a normally closed by-pass valve means serving when open to afford substantially free flow of refrigerant vapor from the condenser to the evaporator and substantially free drainage of refrigerant liquid from the evaporator to the condenser; and means operable to suspend the operation of said energy-actuated means and open said by-pass valve means while maintainin the means for circulating cooling fluid in operation.

4. The combination of a refrigerating circuit containing a volatile refrigerant and comprising an evaporator, a liquid-refrigerant retaining condenser, means for circulating a cooling fluid at a temperature materially above 32 F. in heat-exchanging relation with liquid in the condenser, energy-actuated means for withdrawing refrigerant vapor from the evaporator and delivering it at higher pressure to the condenser, and means serving to maintain a pressure differential between the condenser and the evaporator while supplying liquid refrigerant from the former to the latter; a normally closed by-pass valve which when open affords substantially free flow of vaporous refrigerant from the condenser to the evaporator; a normally closed by-pass valve which when open affords substantially free drainage of liquid refrigerant from the evaporator to the condenser; and means operable to suspend the operation of said energy-actuated means and open both said by-pass valves while maintaining the means for circulating cooling fluid in operation.

5. The combination defined in claim 4 in which the energy-actuated means is a compressor driven by an electric motor, and the by-pass valves are solenoid-actuated in their opening directions and a single switch is provided to energize the solenoid and the motor selectively.

MELDON G. LEESON.

REFERENCES CITED UNITED STATES PATENTS Name Date Ruppricht Aug. 5, 1936 Number 

